Process of making glyoxylic acid or its compounds.



IvI. vAYGoUNY.

PROCESS 0F MAKING GLYOXYLIC ACID 0R ITS COMPOUNDS.

APPLICATION FILED IuLY 2a, I9Io.

LQQW/QCQ Paten-ted May 29, 191.7.

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MOOSHEGH VYGOUNY, OF BERKELEY, CALIFORNIA, ASSIGNOR 'IO ROYAL IBAKING i POWDER COMPANY, 'A CORPORATION OF NEW JERSEY.

PROCESS OF MAKENG GLYOXYLIC A OED OR ITS COMPOUNDS.

Specification of Letters Patent.

Application led July 23, 1910. Serial No. 573,545.

To all wwm t may concern:

Be it known that l, MoosHEGH VAYGOUNY, a citizen of the United States, residing at Berkeley, county of Alameda, and State of California, have invented a new and useful Process of Making Glyoxylic Acid or lts Compounds, of which the following is a specication..

This invention relates to a process of making glyoxylic acid or its compounds from oXalic acid or its compounds and has as its object the making of glyoxylic acid or its compounds in a'more economical and ecient manner than heretofore.

My process comprises the reduction of oxalic acid or its compounds by means of .amalgams properly generated and used.

Heretofore it has not been practicable to y make glyoxylates for commercial purposes '20 by the reduction of oxalates by means of amalgams, and l believe that ll am the first to develop an available method which may be successfully and economically practised.

ll describe my process in connection with the accompanying drawing showinga form of apparatus lwherein the amalgam desired is made electrolytcally in one chamber and used in another chamber. The drawing is a diagrammatic representation of a double compartment cell wherein both the formation of the amalgam and its decomposition are carried out in a compact manner though still inseparate chambers. lt is intended to be illustrative only as it is obvious that the particular form of apparatus lis not an essential features of the process.

ln the drawing, A. indicates a suitable vessel, which may be made of any desirable non-conducting material, such als wood, of cylindrical, rectangular or other suitable shape, here shown as cylindrical. rlhe bottom of vesseLA may be made of asuitable metal, such as iron, in order to facilitate the cooling of the contents of the vessel ex-` ternally if necessary. ln such case the vessel should, of course, be suitably insulated. B indicates a layer of mercury completely covering the bottom of'vessel A.. C indicates a vessel of non-conducting material, conforming in shape with vessel A, open top and bottom, the bottom portion dipping into mercury B and reaching' to nearly the bottom of vessel A. Vessel C may be supported in this position in any convenient manner. D represents an electrolytic cham- Patented May 29, illilf.

ber constituted by the space between vessels u A and C. E indicates a purely chemical or reaction chamber within vessel C. Chambers D and E are separated and kept so separated from each other bythe layer of mercury B, which acts as a seal, so that the solutions in the two chambers cannot communicate with each other. F indicates 'a suitable insoluble anode, such as platinum, and G- the cathode terminal, the mercury B acting as the cathode. H indicates a suitable stirrer, supported and operated in any convenient manner, the function of which is to keep the solution or mixture to be re` duced in a thorough state of agitation.

With a cell thus constituted, a suitable electrolyte, such as a strong solution of potassium hydrate, is introduced into the electrolytic chamber D, While E receives a mixture of oXalic acid or oXalates and a certain proportion of a strong acid, such as sulfuric acid. As a direct current is made to flow from the anode F to cathode B, an amalgam will form in the mercury within the chamber D. By diffusion, assisted mechanically by stirrer H, or by rocking the cell, if necessary, this amalgam is caused to travel from chamber D to reaction chamber E. Here the amalgam is rapidly attacked by the so lution to be reduced, tending thereby to generate potassium hydrate and hydrogen. T he potassium hydrate becomes neutralized by the free acids'prcsent, while the hydrogen tending to be liberated, acts at once in that nascent state and under the conditions obtaining, upon one of the carboxyl groupings of the oxalic acid molecules, thereby converting or reducing the latter into glyoXylic acid in a very satisfactory manner. During the process of this reduction the contents of the reaction chamber are kept in a state of vigorous agitation, while simultaneously they are kept cool by means of a suitable cooling device applied either externally or internally, the object of the cooling being merely to keep the temperature of the reacting agents atabout '7 to 10 Centigrade throughout the operation of the reduction of the oxalic acid.

ln order to make clear the method of oping to about 90 grams of the anhydrous acid, and about 100 grams of sulfuric acid (in addition to that which would correspond to the amount necessary to free the oXalic acid-'in the potassium oxalates, if these were used) is introduced into the reaction chamber. About 400 cu'bic centimeters of a solution of a suitable potassium compound, such as potassium hydrate of such strengthras to Contain about 150 grams of potassium hydrate, being now introduced into the electrolytic chamber, a current of about l2 amperes is caused to flow from anode to cathode through the electrolytic chamber. As this current flows, the amalgam formed passes or is made to pass into the reaction or reduction chamber as descri'bed, where the oXalic acid is rapidly reduced to glyoxylic acid in nearly theoretical quantities under the favorable influence of the excess of sulfuric acid, vigorous agitation and low temperature, brought about as hereinbefore mentioned. In about five hours and a half the evolution of free hydrogen becomes brisk owing to the disappearance of the oxalic acid present. The resulting solution in the reaction cham'ber is now found to be substantially an acid solution of a glyoXylate (in this case potassium glyoXylate) representing the bulk of the oXalic acid which has disappeared; although there is also present in the solution a small amount of further reduction products, together with some other com ounds.

T is solution is now in condition to be used for many of the ypurposes for which glyoxylic acid or its compounds may be employed (rst suitably neutralizing the eX- cess of acidity, if necessary). In order to recover the glyoXylic acid in the said solution, if desired, this latter is further worked up in any suitable manner. Thus, the solution may be first neutralized with the necessary amount of an alkali, such as potassium hydrate, and the resultant solution evaporated down -by heat under reduced pressure. rIhis operation causes first, the excess of potassium sulfate to crystallize out, which is then removed by filtration. 'Io the filtrate is added a small amount of a calcium salt, such as calcium sulfate, in order to precipitate out the further' reduction products present. As the resultant filtrate is now found to consist lof a solution of potassium glyoxylate almost exclusively (that is, if the process of reduction has been carried out carefully), all that now remains to be done is to evaporate it down to crystallization under reduced pressure; or else a further quantity of a calcium salt is added to the same and the calcium glyoXylate formed is filtered loff and further purified. From this may then be obtained free glyoXylic acid by decomposing it with the calculated quantity of sulfuric acid, or, better still, oXalic acid, and

carefully evaporating down the resulting iltered solution of free glyoXylic acid under reduced pressure.

While I have illustrated my process in connection with the use of potassium hydrate, which I have found to be preferable, I do not limit myself to the use of that or any other compound of potassium, as the salts of other metals, such as sodium, ammonium, aluminium or magnesium, may be used. And where I use the term alkali in the claims, I intend to include alkalineearth metals as well as alkali metals.

In order that the process illustrated by the foregoing may be the more successfully practised in the various forms which it may be desirable to give it to meet particular commercial conditions, I direct attention to certain special precautions or conditions which are of importance and are, I believe, entirely novel and original with me:

1st. rI he amalgam brought in contact With the solution or mixture to be reduced should be dilute, otherwise the reduction is very irregular and unsatisfactory.

2nd. Potassium amalgam constitutes a better reducing agent than' any other amalgam. Y v

3d. The solution in the reduction chamber should be freely acid throughout the duration of the reduction. For this purpose it is not adequate that the solution contain free oXalic acid, but it should also contain a good excess of a stronger acid, such as hydrochloric or sulfuric acid. Should such a stronger acid be absent or even present in insufficient amounts, the reduction of the oXalic molecule to the glyoxylic molecule will go on only very desultorily, a point being soon reached where, owing to the conversion of one of the carboxyl groupings in the oXalic molecule into the aldehyde grouping which characterizes glyoxylic acid, the solution is first brought to neutrality and then further to alkalinity (before the oXalic acid has been adequately reduced), owing to the increasing amounts of amalgam being decomposed. Now, under these latter conditions, the o Xalic molecule is no longer reduced; on the contrary, the amount of glyoXylic acid formed in the earlier part of the .work now becomes reduced furtherto glycolic acid, a reduction which I have found does not take place appreciably so long as the solution containing glyoXylic acid remains strongly acid in reaction. Besides this further reduction, there enters here another objectionable factor, to wit: As the free alkali becomes accumulated in the solution or mixture, the glyoXylic acid itself tends more and more easily to be decomposed, purely chemically, into an equal number of molecules of oXalic and glycolic acid.

4th.V The solution even if very strongly acid, should at ,all times be kept at a low Lesmo@ temperature never much exceeding 15o centigrade, but also not falling much below 0, the optimum being 7 to 10". The penalty in case the temperature is allowed to rise much above 15 is that at such higher temperatures glycolic acid begins to be formed, while, on the other hand, at very low temperatures, the reducing action of the amalgam is unduly weakened.

5th. Care should be taken to keep the solution or mixture of oxalic acid or oxalate and sulfuric acid well stirred throughout the duration of the reduction. Should the solution or mixture be allowed to remain quiescent any length of time, a layer is formed near the surface of the subjacent amalgam wherein the conditions warned against in clause 3d Obtain, with consequent further reduction.

6th. rlhe amount of oxalic acid or oxalate to be employed for a given volume of solution should not greatly exceed 15 to 2O grams (calculated as anhydrous oxalic acid) per 100 cc. With larger amounts of oxalic acid there is a noxious tendency to further reduction on the part of the glyoxylic acid formed under the influence of the amalgam present, and this tendency is present even if correspondingly larger amounts of sulfuric acid are used at the outset.

Among the important advantages of practising my process in the preferred form above described are First-By carrying on the reduction of the oxalic acid in a chamber separated from the electrolytic action instead of directly in an electrolytic cell wherein the mercury would act as a cathode, l avoid the destruction of the current at the anode, which the use of such cells necessarily would involve (even if porous diaphragme were introduced) to such an extent as to render that arrangement unsuited for practical manufacturing purposes.

Second :-So. too, by employing amalgams formed electrolytically, l avoid the disadvantages which would necessarily be involved in using purely chemically prepared amalgams, such as the further oxidation products both of the mercury and the other metals employed, which would tend to diminish the eiiiciency of the hydrogen generated; and this, moreover, would involve cumbersomeness, lack of economy and unsuitability to practical operation.

ln order to obtain the most satisfactory results the amalgam should be made electrolytically and decomposed chemically in a chamber wherein electrolysis does not take place.

What ll claim, is

l. A process of making glyoxylates, com` prising the reduction of oxalic acid or its compounds by means of the reaction of an amalgam in dilute form on a hydrogen-containing substance.

2.A process of making glyoxylates, comprising the reduction of oxalic acid or its compounds by means of the reaction of an amalgam on a solution thereof comprising a hydrogen-containing substance and not exceeding 25 grams of oxalic acid or oxalate (calculated as anhydrous oxalic acid) per 100 cc.

3. A process of making glyoxylates, comprising the reduction of potassium oxalates in a solution containing water, in the presence of sulfuric acid, by means of an amalgam.

4. A process of producing glyoxylic acid and glyoxylates which comprises producing an amalgam of an alkali metal by the action of an electric current and continuously transferring portions of said amalgam into contact with an acid aqueous solution containing dissolved oxalic acid.

5. rllhe process of producing glyoxylic acid which comprises producing a potassium amalgam by the action of an electric current and continuously transferring portions of said amalgam into contact with an acid aqiaous solution containing dissolved oxalic aci 6. A. process of making glyoxylic acid and glyoxylates, comprising the reduction of oxalic acid or its compounds by means of the reaction of a suitable amalgam formed electrolytically on a hydrogen-containing substance.

7. A process of making glyoxylic acid and glyoxylates, comprising the reduction ofi oxalic acid or its compounds by means of the reaction of a suitable amalgam on a hydrogen-containing substance, in the presence of free mineral acid.

8. A process of making glyoxylic acid and glyoxylates, comprising the :reduction of oxalic acid or its compounds by means of the reaction of a suitable amalgam on a hydrogen-containing substance at a temperature below 20 C.

9. A process of making glyoxylic acid and glyoxylates, comprising the reduction of oxalic acid or its compounds by means of the reaction of an amalgam in dilute form on a hydrogen-containingsubstance, in the presence of free acid, at a temperature between zero and 20 C.

lln testimony whereof ll have signed this specification in the presence of two subscribing witnesses.

ivroosnroii vareormr.

Witnesses LESTER K. JACOBS, K. Gr. LE ARD. 

